81221128 has 8 divisors (see below), whose sum is σ = 152289630. Its totient is φ = 40610560.

The previous prime is 81221117. The next prime is 81221159. The reversal of 81221128 is 82112218.

It can be written as a sum of positive squares in only one way, i.e., 60808804 + 20412324 = 7798^2 + 4518^2 .

It is a tau number, because it is divible by the number of its divisors (8).

It is a nude number because it is divisible by every one of its digits.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5076313 + ... + 5076328.

Almost surely, 2^81221128 is an apocalyptic number.

It is an amenable number.

81221128 is a deficient number, since it is larger than the sum of its proper divisors (71068502).

81221128 is a wasteful number, since it uses less digits than its factorization.

81221128 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10152647 (or 10152643 counting only the distinct ones).

The product of its digits is 512, while the sum is 25.

The square root of 81221128 is about 9012.2765159531. The cubic root of 81221128 is about 433.0682439146.

The spelling of 81221128 in words is "eighty-one million, two hundred twenty-one thousand, one hundred twenty-eight".